Components in or for self-powered vehicles

ABSTRACT

Components in or for self-powered vehicles, including in particular an integrated power unit in which a reciprocating-piston internal combustion engine and a item in which the engine cylinders and the principal rotary plane which lies normal to the cylinder axes and includes the engine crankshaft axis. Compactness and simplicity are further promoted by designing the casing structure of the power unit to include an indivisible main component which encases parts of both the engine and the transmission system. The invention also includes features combined with and/or related to such a power unit, including a specific design for the transmission system, an arrangement of the induction system for the engine, installation arrangements for the power unit within vehicles, and related vehicle suspension systems.

This invention relates to self-powered vehicles, and to novelarrangements in or for them of integrated power units, internalcombustion engines, rotary transmission systems, suspension systems andmounting systems, such arrangements individually or in combinationpromoting compactness and simplicity and improved efficiency generally.

The integration of engine, gearbox and final drive into a single unitlocated adjacent to the driven wheels is an established automotivedesign technique which tends to result in reduced weight and cost, andimproved transmission efficiency. The placement of the unit in atransverse position (i.e. with the crankshaft parallel with the virtualaxles of the car) is also well established and tends to result in moreefficient space utilisation within the vehicle envelope, with furtherimprovement in transmission efficiency due to the elimination of aright-angle drive.

Most existing arrangements of transverse power units fall into two basiccategories. Firstly, those with the engine placed mainly above thetransmission components, but substantially central within the width ofthe vehicle, and secondly, those where the transmission is to one end ofthe engine crankshaft, such that the whole forms an assembly which isasymmetric relative to the vehicle longitudinal centre line, with theresult that, unless special measures are taken, the drive shafts to thetwo wheels will be of unequal length.

Such power units are more commonly intended for applications in vehiclesdriven through their front wheels, such as passenger saloon cars ofsmall to medium size. However, with rising power to weight ratios, frontwheel drive becomes increasingly undesirable due to considerations oftraction, and therefore, particularly in cars of higher performance, anintegrated power unit located adjacent to the rear wheels may be moreadvantageous.

Various drawbacks and limitations are apparent in existing transversepower unit designs, particularly with regard to rear drive applications.

In passenger saloon cars, and more particularly those of the so called`hatchback` variety, and in estate car derivatives, where it isdesirable that the passenger compartment should be freelyinterconnectable with the rear luggage compartment, such that, bysuitable means, the entire rear portion of the body may be converted toan unobstructed load-carrying space having a substantially flatplatform, the existence adjacent to the rear wheels of a power unit ofthe profile typical of existing designs may render such provisionineffectual, especially where the engine is above the transmission. Asimilar drawback applies in the case of commercial vehicles. Also, insports cars, wherein the location of an integrated power unitimmediately behind the occupants is particularly advantageous, both withregard to traction in a high performance application and also to themarketing appeal of a configuration akin to that of current racing cars,existing examples serve to illustrate the difficulty of providingadequate luggage capacity anywhere within the vehicle, and also ofproviding stowage for small items within the passenger compartment, asis desirable in the interests of convenient usage. The space required toaccommodate an efficient induction system to the engine may particularlyexacerbate these difficulties. Meanwhile, unless measures are taken tominimise the mass of a rear-mounted power unit, vehicle stability andhandling problems may arise due to an excessive rearward weight bias.

Even in front engine applications, existing transverse power units,especially those having the engine above the transmission, may suffer adrawback in that the height, occurring at a point far forward in thevehicle, may impose restrictions on the provision of bodywork havingfavourable aerodynamic properties.

A further consideration in any design incorporating an integrated powerunit is that additional benefit may derive from mounting the suspensionsystem of the adjacent wheels direct to the power unit, the wholeresultant assembly then being flexibly mounted to the vehicle structure.By a suitable selection of mounting flexibilities, the power unit massmay thus be made to act as an effective dynamic absorber of road-inducedvibrations. Such an arrangement may also permit substantial reductionsin weight and cost, providing that it can be achieved with a minimumadjunction of material to the power unit structure, such as brackets andsubframes. Also, in rear drive applications, further advantage,particularly to weight and cost, may accrue by utilising the final driveshafts as part of the suspension linkage, but this is feasible onlywhere the two shafts are of equal and suitable lengths. Existing powerunits are not known to have been designed with the above provisionsspecifically in mind, the requirements of which may be more easily metin arrangements where the main engine structure and the final drivegears are both located substantially central within the width of thevehicle.

In certain applications, such symmetry may also be desirable foraesthetic or other reasons, such as to permit the use of an enginehaving more cylinders in line across a vehicle of given width. Also, infront drive applications, the use of an asymmetric arrangement whereinthe drive shafts to the two wheels are of unequal lengths may result inundesirable disturbances being felt through the steering wheel,particularly in more highly powered vehicles.

A further drawback of known existing power unit designs, and moreparticularly of those which do offer the advantage of substantialsymmetry, concerns the efficiency of the gear transmission system. Animportant consideration in the design of any vehicle transmissiongearing is to minimise the total number of gear meshing points betweenthe engine crankshaft and the driven road wheels, since at each meshingpoint, useful power will be lost while unwelcome noise may be generated.This consideration may be regarded as especially cogent in the case ofan integrated transverse power unit if full advantage is to be taken ofthe inherent efficiency benefits mentioned in the opening paragraphs.

It may be shown of typical existing designs having manually operatedgearboxes, that the practical minimum total number of such meshingpoints is two, as is achieved by means of a widely favoured arrangementof the asymmetric variety, wherein a gearbox of the `two shaft` (or `alldirect`) type is located to the end of the engine, with its input shaftcoaxial with the engine crankshaft, drive in each of the forward ratiosprovided then being simply through one of a number of alternativelyselectable gear pairs, the only other gear meshing point occurring atthe final drive gears which normally are additionally provided, both tobring the output to a convenient point and also since the required lowratios cannot usually be provided in a single step.

In power units of the more symmetrical variety, where the gearbox inputshaft is not coaxial with the engine crankshaft, a primary drive meansmust be provided, which may take the form of two or more gears or achain drive, and which therefore adds a further source of inefficiency.In an existing design of this type, a total of two meshing points isagain achieved, but only in one of the forward ratios provided, by meansof a design where the primary drive consists of a single pair of gears,while the gearbox is of the `three shaft` (or `direct top` or`layshaft`) type, such that the input and output shafts are coaxial andmay be joined together to provide a direct straight-through drive as oneof the selectable ratios, the second meshing point then again occurringat the final drive gears which are also provided. However, a drawback ofthis arrangement is that, when any of the other forward ratios areselected, two additional meshing points occur within the gearbox asdrive is transferred to and then back from the layshaft.

This disadvantage is more manifest where, in an arrangement of thistype, it is required to incorporate a gearbox having, for example, fiveforward speeds, and of the type being increasingly favoured in theinterests of fual efficiency where the two highest forward ratios areboth intended to be used extensively, since if fourth gear is made`direct`, fifth would involve at least four total meshing points, andvice versa.

If, in a power unit having a primary drive means, a gearbox of thealternative `two shaft` variety is used, the practical minimum totalnumber of meshing points achievable is three in all gears, one more thanthe optimum. A further disadvantage of any power unit arrangementutilising a manual gearbox of the `two shaft` variety is that this makesit more difficult to provide for the optional employment of an automaticgearbox of conventional form.

Further concerning existing transmission systems, the number ofcomponents, particularly gears, each different from any other, isusually considerable, and the cost of manufacture is therefore high.

An aim of the present invention is to provide an improved arrangementfor an integrated automotive power unit which includes a reciprocatingpiston internal combustion engine, a transmission system and allnecessary auxiliary equipment, such that the overall profile,particularly as viewed in a direction along the crankshaft axis, isminimised and of a shape suitable, for example, for incorporation into acompact sports car or high performance saloon car wherein drive is to beprovided through the rear wheels and wherein a favourable arrangement ofpassenger and luggage accommodation is to be provided, it being intendedthat the power unit should be disposed in such application with itscrankshaft transverse and its main structure arranged approximatelysymmetrical with respect to the longitudinal centre line of the vehicle.A further aim of the invention is to provide a manually operated gearedtransmission system arranged so that the connections to the final driveoutput shafts to the wheels may also be symmetrically disposed withrespect to the aforementioned centre line, and also arranged, in theinterests of efficiency, such that all shafting is parallel with thecrankshaft axis, and such that, in more than one of the forward ratiosprovided, the total number of loaded gear meshing points between thecrankshaft and the driven road wheels is only two, and further arrangedsuch that the cost, particularly of the gear elements, may be minimised.It is also an aim of the invention to provide an associated suspensionsystem of simple design which may incorporate the final drive outputshafts as part of its linkage and which is mounted directly to the powerunit so as to form a sub-assembly which may be flexibly mounted to thevehicle structure in a favourable manner. The invention further aims tosatisfy the requirements of lightness, low cost of manufacture, ease ofservicing, structural stiffness, a low centre of gravity, a simplegearchange arrangement and an induction system of favourable form. It isintended that an embodiment of parts of the invention should be equallysuitable for vehicles driven through the front wheels or through four ormore wheels.

With the above aims in view, then, according to the present invention,there is provided an integrated power unit incorporating a reprocatingpiston internal combustion engine and a transmission system, in anarrangement where the engine, having a number of cylinders disposed inline, is designed to operate in a position with its crankshaft axisapproximately parallel to an adjacent virtual axle of a motor vehicle,and with its cylinder axes contained in a plane describing an acuteangle above the horizontal, such that the crankshaft axis is at a levelsubstantially similar to that of the virtual axle while the cylinderhead is located approximately directly over the virtual axle, and withits cylinders disposed either side of the vehicle longitudinal centreline in a substantially symmetrical manner, and with the transmissionbeing accommodated in the main within casings formed beneath thecylinders such that a section which may lie beneath the centralcylinders is extended furthest from the crankshaft and encompasses anaxis substantially coincident with the virtual axle at the normal rideheight and known as the final drive axis, the power unit being designedto be in direct driving communication with the adjacent road wheelsthrough universally jointed drive shafts whose inner ends are connectedwith output driving members of the power unit at points which may besymmetrically disposed either side of the vehicle longitudinal centreline and which lie on the final drive axis, which axis may, by virtue ofthe general arrangement of the power unit, lie in a plane which alsoincludes a joint face between the cylinder block and cylinder head.

These features of the invention afford a particularly compact,favourably shaped assemblage, advantageous not only spatially, but alsoto the provision of a power unit casing structure which is light andstiff and suitable for example to act as a stressed member supportingvehicle suspension loadings.

In an embodiment in which the said casing structure is of a preferabledesign, there is provided a main casing part, formed so as to includecylinder, crankcase and main transmission housings in an integral unit,while there may additionally be provided a combined crankcase andtransmission closing part, a final drive covering part, a cylinder headand end covering parts, such provisions affording a structure ofparticularly high efficiency and low cost, by virtue of the small numberof jointings involved, while at the same time facilitating manufacturingand assembly processes.

The crankcase and transmission closing part may adjoin the main casingpart in a plane including the crankshaft axis, thereby permitting afavourable design wherein the engine main bearings are provided inhousings diametrally split by the joint face such that semi circularportions thereof reside in each of the two adjoining casing parts, thisfeature rendering unnecessary the use of separate bearing caps and atthe same time providing a particularly rigid means of support for thecrankshaft.

Similarly, the final drive covering part may adjoin the main casing partin a plane including the final drive axis, in a design whereby theresultant enclosure constitutes the aforementioned furthest extendedsection of the transmission housing, and such that the aforementionedpower unit output drive members may emerge from the sidewalls of theresultant enclosure, and wherein there may be provided within theresultant enclosure, parts centred on the final drive axis and connectedwith the power unit output drive members, such as a differential andgearing attached thereto, which parts may be supported by bearingsprovided in housings diametrally split by the joint face such that semicircular portions thereof reside in each of the two adjoining casingparts, such a design providing a simple construction of low cost andalso a convenient means of assembly of the final drive parts.

In a particularly advantageous embodiment of the invention, the featuresof the last paragraph are incorporated, together with an aforementionedfeature whereby the final drive axis lies in a plane which also includesa joint face between the cylinder block and cylinder head, and thusthere may be provided on the main casing part a single extended flatsurface designed to serve as an abutment face both for the cylinder headand for the final drive covering part, thereby enabling a furtherreduction in machining costs. Preferably, this face may be machinedparallel with a further facing of the main casing part which may includethe crankshaft axis, and to which abuts the combined crankcase andtransmission closing part, and perpendicular to the cylinder axes.

The cylinder head design may include ports which emerge on the sidefacewhich is adjacent to the transmission parts, and in order then to permita compact juxtapostion of cylinder head and final drive components,particularly in an embodiment which may incorporate the features of thetwo preceding paragraphs, such ports may be provided having a steepdowndraught angle relative to the cylinder axis, such that, where theseare, for example, inlet ports, there may be provided extended inductiontracts which run in a substantially straight line, passing immediatelyabove the final drive parts, but which may yet, due to the generalconfiguration of the power unit, be of an updraught nature, and suchthat their extremities may lie at a very low level outboard of the finaldrive parts. Such provisions are particularly advantageous in the caseof an embodiment designed to be installed in the rear of a vehicle, andwherein the crankshaft is located in front of the final drive axis, andsuch that the extremities of the induction system, being low, may beaccommodated beneath the boot floor of the vehicle, thus permitting theuse of tracts which are long, and thereby favourable to the enhancementof engine output at a lower operating speeds, but which are free ofsharp bends which might inhibit gas flow and hence power at higherspeeds, and which meanwhile cause a minimum of intrusion into areas ofthe vehicle which may be required to accommodate luggage or othercomponents. Also, the inlet ports are thus provided at a favourableangle of approach to the cylinders.

In an embodiment wherein the engine incorporates a fuel injectionsystem, the injectors may be positioned on the upper side of theinduction tracts, at a point approximately directly above the finaldrive parts, and so as to be aimed in a favourable manner almostdirectly down the inlet ports onto the back of the inlet valves, but soas also to be located in a particularly accessible position. Fuelinjection may be a particularly desirable feature of a power unit of thenature herein intended, both in order to further improve overalloperating efficiency, and also to avoid problems such as fuel puddlingwhich might otherwise be caused by the use of an updraught section inthe induction tract, and the aforementioned features provide aparticularly favourable installation.

Both the cylinder head and the crankcase closing part may be retained tothe main casing part by fastening devices such as long bolts, and in anembodiment wherein the cylinder bore and the main bearing diameter aresuitably related, the fasteners for the two components may share thesame axes, and further, there may then be provided singular longfasteners passing right through the main casing part and serving toretain both the cylinder head and the crankcase closing part by linkingthose two parts together, and such fasteners may be provided such thatthey are threaded into the cylinder head from its underside, and suchthat they may be operated from outside the crankcase closing part. Thepower unit configuration proposed herein particularly facilitates suchprovision, which may be especially favourable in embodiments whereinconsiderations related to the design of the cylinder head dictate that acomponent such as a camshaft should be positioned such that it masksaccess to the cylinder head fasteners, as may occur particularly incylinder heads of the four valve per cylinder variety with pent roofcombustion chambers. Such a fastening arrangement may also be favourableto certain installations of the power unit in a vehicle.

The crankcase closing part may be designed such that the chamber inwhich the crankshaft operates is separated from a further lower chamber,in which may be contained lubricating oil, and the main crankchamber maythus be designed such that its internal surfaces are smooth and shapedso as to minimise crankcase windage losses. Furthermore, ports may beprovided linking the two chambers, through which lubricant may return tothe lower chamber, and these ports may be shaped so as to effect anatural continuation of the path of flow of lubricant within the mainchamber, and hence so as to minimise restriction to the return flow,particularly in the case where the crankshaft rotates in a directionsuch that the crankpin moves downwards through the main proportion ofthe crankchamber in the crankcase closing part.

The transmission system may include, in addition to the aforementionedparts on the final drive axis, further parts such as might constitute agearbox, and of which the principal functional elements are arrangedalong axes which may be mutually parallel and which may be called thegearbox axes, which parts may be accommodated within the power unitarrangement in a manner whereby particularly efficient use is made of anavailable space, and such that the parts are contained within a sectionof the aforementioned transmission housing which lies more adjacent tothe crankcase and which may extend beneath the central and outercylinders, and such that the gearbox axes are arranged substantiallyparallel to the final drive axis, and hence also to the crankshaft axis,and such that one gearbox axis, which may be called the gearboxmainshaft axis, may be located approximately midway between the finaldrive axis and the crankshaft axis, all three of which axes may lie onapproximately the same level, while a second gearbox axis may be locatedsubstantially directly below the mainshaft axis. The furthertransmission parts may thus be accommodated entirely within the powerunit profile which is determined by the arrangement of the engine andfinal drive parts, even though this profile is itself very compact. Morespecifically, all of these transmission axes, and also the cylinderaxes, may thus be located on or to the same side of a plane whichincludes the crankshaft axis and which is normal to the common plane ofthe cylinder axes.

In order to effect driving communication between the crankshaft andgearbox mainshaft axes, which latter may also be called the gearboxinput axis, there is provided a primary drive medium, which may belocated to one end of the power unit, and which may take the form of thepair of gears, while there may also be provided adjacent thereto aclutch, preferably centred on the gearbox mainshaft axis, and thusarranged so as to be able to effect driving connection between theprimary drive medium and the gearbox. Arranged thus, the periphery ofthe clutch parts need not, as it might were the clutch centred on thecrankshaft axis, extend outside the profile of the power unit asdetermined by aforementioned components and as viewed in a directionalong the crankshaft axis, not even in the regions where the saidprofile is determined solely by the cross-section of the crankcasestructure, and also, as a result of this arrangement, parts which may beprovided within the transmission system and associated withgearchanging, such as, for example, synchronisers, are not subject tothe inertia of the primary drive parts. The combination of a clutchpositioned thus and a primary drive consisting of only two gears isparticularly favourable, the drive being efficient since only a singlegear meshing point is involved, and more so since the gears maynecessarily be of a large diameter and the loads at the meshing pointthus correspondingly low, and while the inertia value of such gears maybe considerable, the preferred clutch position eliminates anydetrimental effect thereof. Further, since the gears are in permanentdriving communication with the crankshaft, they may contribute aproportion of the flywheel effect required by the engine, and thus allowthe use of a main flywheel of reduced mass, and also, since the flywheeleffect is thus accumulated from contra rotating elements, a smootheridling performance may be expected of the engine. While the dynamicadvantages associated with the combination of a two gear primary driveand a clutch located on the gearbox input axis are applicable to anypower unit requiring a primary drive medium, such features are onlyfeasible in a power unit arrangement such as that provided by thepresent invention, and where the gearbox input axis is at a sufficientlyhigh level to enable the clutch to be provided with adequate clearanceabove the road surface. The preferred positioning of the clutch outboardof the primary drive components is also advantageous with regard toaccess and servicing.

In order that the profile of the power unit, as viewed in a directionalong the crankshaft axis, should not be enlarged by requisite auxiliarycomponents such as an alternator, a starter motor and a distributor,such components may be provided located to the ends of the power unitand extending outwards. In an embodiment wherein the clutch ispositioned on the gearbox input axis, and physically outboard of theprimary drive parts, and is of the dry plate variety, the alternator maybe driven by means of a friction wheel engaging with the outer peripheryof a drum containng the clutch parts, while the starter motor may beprovided able to mesh with a gear affixed to the said drum, and theseauxiliary components may then be arranged so as to lie one above theother, and extending outwards from an area approximately in line withthe end of the crankcase, while the distributor may be driven from oneend of the engine camshaft. In an embodiment wherein the engine isliquid cooled, a coolant pump may be provided driven from a point withinthe camshaft driving mechanism, and the pump may be located at a lowlevel relative to the cylinders and cylinder head, such that coolant mayflow advantageously in a basically upward direction through the engine.An additional advantage of the foregoing features is that there is thusno need for any external belt drive, and further, no need for thecrankshaft to emerge from the end covers of the power unit, and hence noneed for oil sealing devices contacting the crankshaft.

Such sealing means may be provided on the gearbox input axis to protectthe dry plate clutch, and provided the engine and transmission partsshare a common lubricant, the only other seals required are at thepoints where the final drive output members emerge from the transmissionhousings. The power loss associated with oil sealing may thus beminimised.

In view of further aims such as that concerning a small number of loadedgear meshing points, a preferable embodiment of the invention includes atransmission system such as that which is described in the textsubsequent hereto. Whilst being based upon gearbox and final drive axeswhich may be arranged in the manner described in a preceding paragraph,the transmission system may also be used advantageously independently ofthe power unit described herein, for example in integrated power unitsof other configurations or in transaxle devices.

According to this aspect of the invention, there is provided a rotarytransmission system, designed to operate in a motor vehicle as acombined gearbox and final drive mechanism affording a series of overallspeed ratios, and incorporating an input shaft, a layshaft and a finaldrive output component, all rotatable about discrete axes which may allbe arranged substantially parallel with the virtual axles of thevehicle, and incorporating also a set of gears arranged such that atleast two gear pairs of differing ratio are alternatively engageablewith each pair having a driving gear coaxial with the input shaft and adriven gear coaxial with the final drive output component, which gearsmay collectively be termed the final drive gears, while at least onefurther pair of gears is engageable to provide drive from the inputshaft to the layshaft, and at least one pair of gears is engageable toprovide drive back from the layshaft to a part coaxial with the inputshaft.

A transmission system having these features can provide at least twospeed ratios selectable such that in either of them, the drive paththrough the system is direct along the axis of the input shaft to afinal drive driving gear, and thence via the corresponding driven gearto the final drive output component, such a drive path thus includingonly a single gear meshing point between the input shaft and the finaldrive output component, these speed ratios being termed the directratios and each being equivalent to a `top` gear in the case of aconventional three shaft gearbox operating in conjunction with a finaldrive gear pair, while a number of further speed ratios, which may betermed the indirect ratios, may be provided by way of the layshaft,according to any known practice.

In an arrangement which represents a reversal of the practice which ismore usual in layshaft gearboxes in motor cars, a number of indirectgear pairs are provided alternatively engageable between the input shaftand the layshaft, whilst there is also provided on the layshaft aconstant mesh output pinion, engageable with an output gear.

In a particularly favourable embodiment, the output gear referred to inthe preceding paragraph is one of the final drive driving gears.

The features of this embodiment, which are especially suited to thepower unit arrangement disclosed herein, or to other applications wherethe layshaft centre need not lie in a line between the centres of theinput shaft and the final drive output component, can provide a numberof indirect ratios equal to the number of indirect gear pairs, each suchthat when selected the drive path through the transmission system isfrom the input shaft, via the engaged indirect gear pair to thelayshaft, and thence by way of a train of three gears to the final driveoutput component, the central element of the train being the final drivedriving gear in this case operating only as an idler gear between theconstant mesh output pinion and the corresponding final drive drivengear, such a train providing an output path of potentially favourableefficiency. Furthermore, the total number of gears in such an embodimentcan be less than in an equivalent transmission system of a more usualdesign, and the overall length, weight and cost may thereby all befavourably influenced.

In an arrangement which affords a reverse speed ratio in a particularlyadvantageous manner, there is provided on the layshaft a further pinion,which may be known as the reverse pinion, and which is engageabledirectly with a final drive driven gear.

This feature, which again is suited to the power unit arrangementdisclosed herein, or to other applications wherein the shafts can bearranged such that the centres of the input shaft, the layshaft and thefinal drive output component form the vertices of a triangle, canprovide a reverse speed ratio wherein the drive path through thetransmission system is from the input shaft to the layshaft by way of apair of gears which may be an indirect gear pair as aforementioned, andthence directly to the final drive output component by way of thereverse pinion and the final drive driven gear. The feature therebyenables a reverse speed ratio to be provided without the need for anadditional shaft axis and thus without increasing the envelope of thetransmission system, and with only one additional gear being necessary.In embodiments having a number of indirect gear pairs, it is possible,if required, to provide an equal number of reverse speed ratios.

Preferably all the gear pairs in the transmission system should be incontinuous meshing engagement, and in order to effect selection of thevarious speed ratios, there may be provided devices which can connectappropriate gears with their supporting shafts, which devices may besynchronised dog clutches of any known type.

In an embodiment in which the transmission system is of the constantmesh type described above, a number of other preferable features may becombined in a manner which permits further advantage, and thus with theshaft centres being in a triangular arrangement as aforementioned, thereare provided the following: an input shaft which extends the full lengthof the complete transmission system, and which may then be known as themainshaft; two final drive gear pairs each having a driven memberpermanently affixed to the final drive output component and a drivinggear which is a discrete component supported by the said mainshaft; anumber of indirect gear pairs each having one member permanently affixedto either the mainshaft or the layshaft and the mating gear a discretecomponent supported by the other of the two said shafts; a connectingdevice as aforesaid adjacent to each of the final drive driving gearsand to each indirect gear which is a discrete component; a mechanism toensure that only one such device can be connected at a given time; aconstant mesh output pinion engaging with the larger of the two finaldrive driving gears; a reverse pinion engaging with the larger of thetwo final drive driven gears; and a device by means of which thelayshaft can be connected either with the constant mesh output pinion orwith the reverse pinion, which device may be an unsynchronised dogclutch, and in such an arrangement the shaft centre distances and therelevant gear diameters being chosen such that the constant mesh outputpinion cannot contact the final drive driven gear with which it isentrained, and such that similarly the reverse pinion cannot contact thefinal drive driving gear with which it is entrained.

A transmission system having these features may operate as follows: forall forward speed ratios, the constant mesh output pinion is connectedwith the layshaft; for each indirect speed ratio, the connecting deviceadjacent to the appropriate indirect gear pair is engaged, such thatdrive may pass from the mainshaft to the layshaft and thence to thefinal drive output component by way of the constant mesh output pinionand the final drive gear pair entrained therewith, with the driving gearoperating as an idler; for each direct speed ratio, the connectingdevice adjacent to the appropriate final drive driving gear is engaged,such that drive may pass directly from the mainshaft to the final driveoutput component; for a reverse speed ratio an indirect gear pair isengaged as aforementioned, and the layshaft is disconnected from theconstant mesh output pinion and instead connected to the reverse pinion,such that drive may pass from the mainshaft to the layshaft and thencedirectly and in the required sense for a reverse speed ratio, to thefinal drive output component. The transmission system thus does notrequire a gearbox output shaft as such, nor does it require a spigotarrangement such as is common in layshaft gearboxes, and the designthereby facilitates the provision of a favourable mainshaft bearingarrangement.

Preferably the reverse pinion is provided with a static supportive stubshaft, coaxial with the layshaft, in order to avoid possible large speeddifferentials while the forward gears are engaged.

In a preferred design for a five speed and reverse constant meshtransmission, the combination of features just described is embodied,and in order to provide fourth and fifth speeds as direct ratios, thereare provided two only final drive gear pairs of appropriate diameters,together with three indirect gear pairs for the first, second and thirdspeeds, of which that for first speed is utilised in the reverse geartrain.

Whilst providing the two direct upper speed ratios and also the threelower speed ratios having an advantageous drive path, as well asproviding a reverse speed ratio, such a transmission system yetcontains, other than the parts of the final drive axis, only ten gearwheels in total, and these on only two shaft axes, and may thus beparticularly compact and light, as well as of low cost. Furthermore, thearrangement allows the synchronisers for the lower ratios to be providedin positions where the referred inertia of the clutch plate andassociated items, as sensed by the synchronisers, is less than inequivalent transmissions of a more usual design, and hence suchsynchronisers may be comparatively more efficient.

To yet further advantage, the arrangement, particularly when used inconjunction with a primary drive means, lends itself to a featurewhereby the said ten gear wheels are not all of different sizes, even ina transmission system which provides a most favourably spaced series ofspeed ratios, and thus, concerning the indirect gear pairs for secondand third speeds, the mainshaft gear of the one pair may have the samediameter as the layshaft gear of the other pair, and vice versa, andmeanwhile the final drive driving gear for fourth speed may have thelarger of these two diameters, and also the indirect gear pair for firstspeed may bear a similar reciprocal relationship to the gear pair whichcomprises the final drive driving gear for fifth speed and the constantmesh output pinion, and the reverse pinion may also have the smaller ofthese two diameters, the same as the constant mesh output pinion. Thusthe set of ten gears may include gears of only four different diameters.

Moreover, in an embodiment in which the further transmission componentssuch as engagement devices are suitably arranged, those gear wheelswhich are of equal diameter can be made similar in all other respects,and thus the set of ten gears for the five speed and reversetransmission may comprise only four different components, two of whichbeing used twice over and the other two three times over. A furtherreduction in manufacturing cost may thereby result.

In a particular example wherein the speed ratios are chosen to suit asports car and advantageously such that the series of vehicle roadspeeds corresponding to a given engine speed approximately form anarithmetic progression, the set of ten gears is made up only ofgearwheels having twenty-seven and thrity-two teeth, mating with pinionshaving twenty-three and twenty-seven teeth respectively, with, in thefinal drive positions, the gearwheels mating with driven gears havingseventy-seven and seventy-three teeth respectively, and meanwhile aprimary drive is incorporated having a ratio appropriate according tothe road wheel size to provide the required overall speed ratios.

A gear selector mechanism for operating the dog clutches may be locatedin the region beneath the crankshaft and adjacent to the mainshaft andlayshaft, such that in vehicle installations where the crankshaft liesbetween the gearchange lever and the transmission parts, a selectorlinkage of a favourably direct nature can be arranged to pass beneaththe crankshaft.

In an intended application where a transmission system such as thatdescribed above is incorporated in parallel with a transverse engineinto an integrated power unit, which may be configured in the mannerdescribed herein, and where there may then be provided a primary drivefrom the engine to the transmission which consists of only a single pairof gears, again as described elsewhere herein, the engine andtransmission parts may be positioned such that when installed in avehicle, the main power unit structure, and also the final drive outputcomponent, which may be a differential, together with the final drivegear pairs may all be disposed substantially symmetrically about thelongitudinal centre line of the vehicle, and such that there may beprovided equal length final drive output shafts to an adjacent pair ofdriven road wheels, and thus the advantages of such symmetry may beobtained in a transmission system in which fourth and fifth speeds, forexample, are provided with only two loaded gear meshing points in totalbetween the crankshaft and the driven road wheels.

The indirect gear pairs can then all be located to one side of the finaldrive parts, and a particularly favourable installation results, forexample, when the transmission is of the five speed variety describedabove and the engine has four cylinders, whereupon the length betweenthe final drive parts, being located adjacent to the central cylinders,and one end of the cylinder block may be just sufficient to convenientlycontain the three indirect gear pairs and associated components, and theprimary drive parts can be located at this same end of the power unit.

Whilst any power unit of this symmetrical nature is well suited tohaving directly attached a suspension system, including such a system ofthe type wherein the final drive output shafts constitute part of thelinkage, the power unit configuration according to the present inventionmay offer an additional advantage in this context in that, with thecylinder block being inclined above the transmission, the upper portionsof the end faces of the said block are then more nearly directly abovethe final drive shafts.

According to a further aspect of the invention, there is provided asuspension system designed to operate on a non-steered driving wheel ofa vehicle, and designed to be mounted directly to an adjacent drivingunit such as the transverse integrated power unit described herein, inwhich system a universally jointed driving shaft acts also as a lowertransverse member of a linkage, the linkage further comprising an uppertransverse arm and a wheel carrying member, the driving shaft jointsconnecting respectively with an axially supported output shaft of thedriving unit and a wheel hub spindle which is supported in bearings inthe wheel carrying member, while the upper transverse arm is a rigidmember and has its ends connected respectively with the top of the wheelcarrying member and the supporting structure of the driving unit bymeans of pivots whose axes both lie approximately parallel to thedirection of motion of the vehicle, the linkage thus being constrainedto a prescribed articulation only.

Preferably, the upper transverse arm has an effective length less thanthat of the driving shaft. Whilst providing a more favourable geometryof wheel movement, this feature is particularly suited to a matching ofthe suspension system with a power unit of the configuration describedherein, and where the end faces of the cylinder block lie outboard ofthe connections to the output driving members, and furthermore thefeature is advantageous to the provision of an arm of suitable rigidity.

The axes of the pivots on the upper transverse arm may be slightlyangled to provide anti-squat effect, etc., if desired.

Motion of the suspension linkage may be controlled, for example, by acoil spring, concentric with a telescopic damper connected between alower part of the wheel carrying member and the inner fulcrum of theupper transverse arm.

Such a suspension system, whilst able to locate the wheel in alldirections, providing a favourable geometry and being particularlysuited to the present application, is also particularly simple, of lowweight and may be constructed at low cost, these advantages being partlyattributable to the utilisation of the driving shaft to perform a secondfunction, and meanwhile the need for devices which allow the drivingshaft to change its effective length is eliminated. Also, the adjunctionof material required to mount such a suspension to the power unitdescribed herein is minimal.

A further advantage of the suspension system described herein concernsits application to cars of very high performance and to racing cars,wherein it is desirable to provide an undersurface to the bodyworkshaped so as to cause a downward force to be applied aerodynamically tothe vehicle when it is driven at high speed, thereby improving itscornering ability.

The suspension system described herein, being free of any transverselinkage below the drive shaft, would enable such an undersurface to beformed so as to be more effective, especially in embodiments where thespringing medium is also located out of the airstream.

By so mounting the entire suspension system directly to the power unit,favourably accurate control of wheel articulation can be achieved, andmeanwhile economics can be made in the structural design of the vehicle.However, it is desirable that the entire assemblage of power unit andsuspension should be flexibly mounted to the vehicle structure in orderto provide isolation from both power unit and road induced vibrations.

According to a further aspect of the invention, there is provided apower unit mounting system designed particularly to suit a sports carhaving a transverse power unit such as that described herein installedadjacent to the rear wheels, and applicable also to other vehicleswherein the spatial requirements of the system are acceptable, withinwhich system there is provided attached to the front face of the powerunit a substantial beam, which may be of hollow box section and whichextends forwards, for example within the space between the seats of thevehicle commonly called the transmission tunnel, and to a point whichmay be close to a front bulkhead of the passenger compartment, at whichpoint is provided a front flexible mounting connecting the beam with thevehicle structure, while two further such flexible mountings areprovided close to each rear wheel, connecting the power unit casings topoints on the vehicle structure which may be adjacent to a rearbulkhead.

Thus the longitudinal separation of the front mounting from the two rearmountings may be considerable, and since this distance is effective as alever arm in reacting to driving torque, mountings may thus be providedwhich are comparatively more flexible, particularly in a verticaldirection, as may be advantageous in providing more effective isolationof vibrations.

In arrangements where the rear suspension is attached directly to thepower unit, the mounting flexibilities may advantageously be chosen inaccordance with the masses involved such that the power unit mass canact as a dynamic absorber of road induced vibrations.

Meanwhile the beam may itself be utilised for example as a fuel tank,which may thus be located in the centre of the vehicle, in a position ofminimum vulnerability in the event of a collision, and also wherechanges in fuel load have the least effect on vehicle weightdistribution.

Furthermore, the beam may also carry the pivot for a gearchange lever,which pivot may thus be rigidly linked to the power unit structure,thereby facilitating the provision of a favourable gearchange linkage.The combination of this feature and a power unit arranged as disclosedherein and having a selector mechanism positioned as aforementioned isparticularly advantageous to gearchanging, since a rigid connecting linkcan be provided passing beneath the crankshaft in a direct line from thegearchange lever to the selector mechanism.

A reversed form of the mounting system may be used in front drivevehicles.

According to yet a further aspect of the invention, there is alsoprovided a power unit, a rotary transmission system, a suspension systemand a mounting system, or any combination thereof, comprising any novelfeature or concept or novel combination of features or conceptsdisclosed herein.

The invention is further defined by the claims, the contents of whichare to be read as included within the disclosure of this specification,and the invention will now be described by way of example with referenceto the accompanying diagrammatic drawings, in which:

FIG. 1 is a section through an integrated power unit comprising afour-cylinder engine and a transmission system providing five forwardspeeds and reverse the section being taken in a plane that includes theaxis of an outer cylinder and that lies at right angles to thecrankshaft axis.

FIG. 2 is an exterior view of the cylinder head and final drive housingsplit face of the same power unit with the cylinder head and all thecasing parts removed other than the main casing part, the view being inthe direction of the cylinder axes.

FIG. 3 is an exterior view of the same power unit taken in a directionparallel to the crankshaft axis and showing the arrangement of auxiliarycomponents.

FIG. 4 is a detailed section through the transmission system of the sameintegrated power unit in which, for ease of understanding, the finaldrive axis appears as if in the same plane as the mainshaft and layshaftaxes.

FIG. 5 shows the transmission system of FIG. 4 schematically.

FIG. 6 is a diagrammatic section through the power unit of FIGS. 1 to 3taken between the central cylinders and particularly shows the cylinderhead bolting arrangement and the fourth speed final drive gears.

FIG. 7 is another section through the same power unit, showingespecially the arrangement of the fifth speed final drive gears.

FIG. 8 is an outline elevation of the power unit of FIGS. 1 to 7installed adjacent to the rear wheels of a sports car, and equipped witha cylinder head with twin overhead camshafts.

FIG. 9 is an outline elevation of the power unit of FIGS. 1 to 7installed adjacent to the rear wheels of a saloon car, and equipped withan alternative cylinder head with a single overhead camshaft.

FIG. 10 is an outline elevation of a variation of the power unit ofFIGS. 1 to 7, installed adjacent to the front wheels of a saloon car.

FIG. 11 is an outline elevation of another variation of the same powerunit, installed adjacent to the front wheels of a saloon car.

FIG. 12 is an elevation of a rear suspension attached to the power unitof FIGS. 1 to 7 when mounted in a vehicle as in FIGS. 8 or 9, as viewedfrom the rear of the vehicle.

FIG. 13 is a plan view of the rear suspension arrangement of FIG. 12.

FIG. 14 is a side elevation of a mounting arrangement associated withthe power unit and suspension assembly of FIGS. 12 and 13.

FIG. 15 is a plan view of the mounting arrangement of FIG. 14, and

FIG. 16 is an elevation, taken in the direction of the arrow XVI of FIG.1, showing the connections between the power unit, the vehicle in whichit is mounted, and the wheels that it drives and including features alsoshown in FIGS. 14 and 15.

As best seen from FIG. 1 and fron FIG. 2, the power unit 1a comprises aninternal combustion engine 1 and a rotary transmission system 2, andprovides output drive along a final drive axis 3, the transmissionhaving also an input shaft or mainshaft axis 4 and a layshaft axis 5.The crankshaft axis 6 of the engine lies parallel to all of thesetransmission axes and forward of them relative to the direction ofmotion of the vehicle (e.g. item 87a, FIGS. 8 and 9) in which the unit1a is mounted. The cylinders 7 of the engine slope steeply backwardsover the transmission system 2, and their axes lie in a common plane 6a.The power unit structure is based upon a main casing part 8, whichincludes cylinders, crankcase and main transmission housings in anintegral unit. A crankcase and transmission closing part 9 adjoinsthereto in a plane 6b which includes the crankshaft axis 6 and which isnormal to the axes of the cylinders 7, while a cylinder head 10 and afinal drive covering part 11 also adjoin the main casing part 8, bothabutting the same facing 12, with which also coincides the final driveaxis 3, this facing also being normal to the direction cylinder axes.The engine 1 has a crankshaft 14 which rotates about axis 6 in thedirection indicated by arrow 13, and is driven by connecting rods 15from reciprocating pistons 16. It will thus be seen that the final driveaxis 3, the input or mainshaft axis 4 and the cylinders 7 all lie to thesame side of plane 6b which includes the crankshaft axis 6 and lies atright angles to plane 6a. Indeed in the example illustrated, axes 3, 4and 6 all lie within or on the boundary of the same quadrant formed bythe intersection of planes 6a and 6b. According to the invention, such arelationship between the locations of these three axes promotescompactness and other advantages.

Main bearings 17 are provided half in the main casing part 8 and half inthe crankcase and transmission closing part 9. Similarly bearings 18 fora differential unit 19, shown in FIG. 2, are provided half in the maincasing part 8 and half in the final drive covering part 11. The cylinderhead 10 has inlet ports 20 approaching the cylinders 7 at a steepdowndraught angle, and which are fed from long induction tracts 21,which are free of sharp bends, and which are formed, together with aplenum chamber 22, into a manifold 23, which lies at a sufficiently lowlevel to be accommodated beneath the boot floor of a vehicle. Fuelinjectors 24, connected to a source of fuel shown schematically at 24a,are provided in an accessible position, and aimed directly at the backsof inlet valves 25, which are operated by camshaft 26. The arrangementof the exhaust valves and ports is not shown, it being intended thatalternative versions of the engine should have either, for maximumperformance, a cylinder head with twin camshafts and four valves percylinder, or for minimum height and lower cost, a cylinder head with asingle camshaft and two valves per cylinder.

The arrangement of bolts 27 for the cylinder head 10 and the crankcaseand transmission closing part 9 is shown in FIG. 6, from which it can beseen that the camshaft 26 would otherwise mask access to the bolts andprevent removal of the cylinder head 10 and associated parts as acomplete assembly. Additional subsidiary attachment bolts (not shown)would be provided for both the crankcase and transmission closing part 9and the cylinder head 10, to allow either to be removed without theother being disturbed.

Meanwhile the crankcase and transmission closing part 9, as seen inFIGS. 1 or 6, is split into two separate chambers, the upper crankshaft28 having a smooth internal form to reduce windage, while the lowerchamber 29 contains lubricating oil and thus acts as a lubricant sumpfor the upper crankchamber 28, ports 30 being provided to allow oil toreturn from the crankchamber 28 to the lower chamber 29 and beingarranged tangentially so as to effect a natural continuation of the pathof flow within crankchamber 28. The lubricating oil, which is used forboth engine and transmission, is also contained in the bottom of themain casing part 8 and the final drive covering part 11. It iscirculated by a pump (not shown) concentric with the crankshaft 14, in acircuit which includes a main oil gallery 31. Also concerninglubrication, in FIG. 2 is shown a passage 32 by means of which oil maydrain from the cylinder head 10 into the transmission housing part ofthe main casing part 8.

FIG. 2 shows two final drive driven gears 33 and 34, attached to thedifferential unit 19 in an arrangement symmetrical with respect to thecylinders 7. At the end of the engine FIG. 2 also shows primary drivegears 35 and 36 by means of which drive is transferred from thecrankshaft axis 6 to the mainshaft axis 4, and a clutch unit 37, centredon the mainshaft axis 4, and having starter gear teeth 39 on theperiphery of a drum 38. The end covers of the power unit are not shownin this view, but the cover at the primary drive end contains an oilseal acting on the surface 40 between the primary drive driven gear 36and the clutch unit 37, which is the dry plate type.

As can be seen from FIG. 3, auxiliary components are arranged at the endof the power unit where the clutch unit 37 is located, there being analternator 41 driven from the drum 38 of the clutch unit 37 by means ofa friction wheel (not shown), and also a starter motor 42 engageablewith the teeth 39. Integral with an end cover 43 is a housing 44containing a pivot pin and bearings for a rear suspension upper link,this pivot lying above the drum 38 of the clutch unit 37. A distributor45 is driven directly from the end of the camshaft 26.

FIGS. 4 and 5 reveal the arrangement of the components of thetransmission system 2 along axes 3, 4 and 5, FIG. 5 being a schematicrepresentation only and FIG. 4 also being a simplified representation:in both figures the axes 3, 4 and 5 appears as if in a single plane,whereas their true relationship is as shown in FIGS. 1, 6 and 7. Besidesthe differential unit 19 and the gears 33 and 34 attached thereto, allcentred on the final drive axis 3, the transmission can also be seen tohave, on the appropriate axes 4 and 5 respectively, a mainshaft 46 and alayshaft 47. The mainshaft 46 is supported by bearings 48, 49 and 50,while the layshaft 47 is supported by bearings 51 and 52. At its inputend, the mainshaft 46 carries on a bearing 53 the assembly of theprimary drive driven gear 36 and the clutch unit 37, and is driventherefrom through a spline 54, the clutch unit 37 being constructedaccording to conventional art and having a driven plate 55 which isclamped between the drum 38 and a pressure plate 56 by means of adiaphragm spring 57. At its other end the mainshaft 46 carries finaldrive driving gears 60 and 61, on bearings 58 and 59 respectively, andis connectable to either by means of a sliding dog clutch 62. The latteris shown for simplicity without any synchronising devices, though suchwould normally be provided according to known practice, and it would becontrolled from the vehicle gearchange unit (not shown). The drivinggears 60 and 61 are in mesh with the driven gears 33 and 34respectively, these gear pairs when engaged by the dog clutch 62providing the direct drive for respectively the fifth and fourth of thefive forward speeds provided.

The final drive driving gear 60 is also in mesh with a constant meshoutput pinion 63, which is carried on a bearing 64 on the layshaft 47,and which is connectable with the layshaft 47 by means of anunsynchronised sliding dog clutch 65. The dogged connection between thelayshaft 47 and the pinion 63 is maintained engaged for all forwardspeeds, the layshafts 47 then being in constant mesh with the outputelements of the transmission system. In the indirect first, second andthird speeds, the layshaft 47 drives the differential unit 19 throughthe train of gears 63, 60 and 33, with the dog clutch 62 being in itsneutral position so that the gear 60 acts as an idler. To provide inputdrive from the mainshaft 46 to the layshaft 47 for these indirect speedratios, the mainshaft 46 carries driving gears 66, 67 and 68, while thelayshaft 47 carries, respectively enmeshed therewith, driven gears 69,70 and 71. The gears 66 and 67 are fast with the mainshaft 46 while thegear 71 is fast with the layshaft 47. The gear 68 is carried on themainshaft 46 by a bearing 72, and is connectable to the mainshaft 46 bymeans of a sliding dog clutch 73, in order to provide the third speed.Similarly the driven gears 69 and 70 are carried on the layshaft 47 bybearings 74 and 75 respectively, and either is connectable with thelayshaft 47 by means of a sliding dog clutch 76, in order to providefirst or second speeds respectively. The dog clutches 73 and 76 areshown for simplicity, like the dog clutch 62, without theirsynchronising devices, and similarly likewise are controlled from thevehicle gearchange unit.

The unsynchronised sliding dog clutch 65, is also used for connectingthe layshaft 47 with a reverse pinion 77, which is carried on a bearing78 on a stub shaft 79, co-axial with the layshaft 47. Although notapparent from FIGS. 4 or 5 due to the simplified representation usedtherein, the reverse pinion 77 is actually in mesh with the final drivedriven gear 34, as indicated by the dotted line 80.

FIGS. 6 and 7 show the true relationships of the gears 34, 61 and 77,and 33, 60 and 63 respectively, and thus it is apparent from FIG. 7 howthe constant mesh output pinion 63 is in mesh with the final drivedriving gear 60, but clear of the corresponding driven gear 33, whileFIG. 6 shows how the reverse pinion 77, while being in mesh with thefinal drive driven gear 34, is clear of the corresponding driving gear61.

The pinions 63 and 77 are of equal size, a common component withseventeen teeth being used for both of these items, and the samecomponent is also used as the first speed driving gear 66. In a similarmanner, a common component with thirty-two teeth is used for both ofgears 60 and 69, a common component with twenty-seven teeth is used forgears 61, 68 and 70, and a common component with twenty-three teeth isused for gears 67 and 71. The set of ten gears on the axes 4 and 5 isthus made up from only four different components. The final drive drivengears 33 and 34 have seventy-three and seventy-seven teeth respectively,and in the illustrated embodiment the primary drive gears 35 and 36 haveforty-eight and fifty-three teeth respectively.

In order that the first speed gear 66 can be commonised with pinions 63and 77, and also because of considerations of desirable diameters, thegear 66, as shown in FIG. 4, has a plain bore where it locates on themainshaft 46, and is driven therefrom by means of a splined dog couplingring 81, the whole mainshaft assembly being clamped together by a nut82. FIG. 4 also shows how the differential unit 19 is splined to outputshafts 84 which are supported by bearings 85. Meanwhile, FIGS. 1, 6 and7 also indicate elements of a gear selection mechanism of known typewhich includes selector rods 86 and an assembly of concentric cam drums87.

FIG. 8 to 11 exemplify installations of the power unit in vehicles eachindicated generally by reference 87a.

In FIG. 8 is shown a two seater sports car 87a in which the power unit1a is fitted immediately behind the seats and drives the rear wheels.The profile of the power unit is seen to be especially suited to thisparticular application, being of a wedge like form which correspondswith the shape of the recess which exists beneath and behind a slopingbulkhead 88, such that spatially efficient packaging of the vehicleelements is facilitated. As a result, the rear luggage space 89 is seento be comparatively large for a car of this type, and also, due to thelowness of the power unit, a shelf 90 can additionally be provided forthe stowage of small items, and is accessible from within the passengercompartment. Seat headrests 91 are hinged to pivot to positions 91a tofacilitate such access, while a division 92 between the shelf 90 and theluggage space 89 is adjustable in position to allow the relative sizesof the two areas to be varied as required. Meanwhile it can be seen thatthe power unit arrangement allows the induction system to beaccommodated with the manifold 23 beneath the boot floor and thus notencroaching into useable luggage space. Also, the power unit, which hasa twin camshaft cylinder head, is seen to be located such that itscentre of gravity would lie favourably within the vehicle wheelbase.

In FIG. 9 is shown a four seater saloon car 87a which is of the`hatchback` type, in which the power unit 1a, equipped with a singlecamshaft cylinder head for minimum height, is again fitted to drive therear wheels, and yet due to its lowness is accommodated beneath a rearluggage platform 93 which is little higher than that in correspondingfront drive cars. The luggage platform would be extendable by foldingthe rear seats, as is conventional in such vehicles, while a further andpreferably invisible luggage space could be provided at the front of thevehicle.

In FIGS. 10 and 11 are shown two examples where the power unit 1a inslightly modified form is installed to drive the front wheels of asaloon car 87a. As shown in FIG. 10, the power unit is fitted in areversed configuration with its crankshaft behind the final drive axis.In order to have the correct direction of rotation of the output driveshafts, either the direction of rotation of the crankshaft would have tobe the reverse, relative to the rest of the power unit, of thatindicated by arrow 13 in FIG. 1, or the primary drive gears 35 and 36would have to be replaced by a chain drive or have an idler gearinterposed. As shown in FIG. 11, the engine has its crankshaft ahead ofthe final drive axis, but, for greater convenience of installation, hasa different type of cylinder head such that the induction manifold 23can be of a downdraught nature. In both of the examples shown in FIGS.10 and 11, the configuration of the power unit can permit either anexceptionally low and aerodynamic bonnet line, or the provision of afront luggage space as aformentioned above the power unit.

In all of the examples shown in FIGS. 8 to 11, the power unit would beinstalled centrally within the width of the vehicle, so that variants ofthe illustrated designs with a greater number of cylinders in line couldbe similarly accommodated.

As depicted in FIGS. 12 and 13, the rear suspension of a wheel 112 ofthe vehicle comprises an upper transverse arm 94, a wheel carrier 95 anda final drive shaft 96 which acts as a lower transverse arm and hasuniversal joints 97 at either end. The arm 94 has at its inner end apivot pin 98 supported by bearings 99 in the housing 44 of the powerunit end cover 43, while at its outer end another pivot pin 100 carriesbearings 101 held in the wheel carrier 95. The arm 94 and the wheelcarrier 95 are both substantially proportioned members, whilst thebearings 99 and 101 are of the taper roller type, such that theassemblage of the arm 94 and the carrier 95 is able to sustain vehicletractive forces.

The universal joint 97 of a drive shaft 96 is connected, at its innerend to the differential output shaft 84 (seen also in FIG. 4, supportedby bearing 85) and at its outer end to a wheel hub spindle 102.Articulation of the linkage is controlled by a spring-damper unit 103connecting the wheel carrier 95 to an extension of the inner pivot pin98. The suspension unit shown in FIGS. 12 and 13 is designed for thatside of the power unit on which the primary drive is located. On theopposite side, the suspension is similar, except that a housingequivalent to 44 is formed on the opposite end cover (not shown) of thepower unit.

The arrangement for mounting the power unit and rear suspension assemblyinto a vehicle is shown in FIGS. 14 and 15. A beam 104 is attached tothe front of the power unit and has at its forward end a flexible frontmounting bush 105 by which it is connected to the vehicle structure. Twofurther rear mounting bushes 106 are fitted into arms 107 which areformed as extensions of the end casings of the power unit. The beam 104is of hollow box section such that a space 108 can be used as a fueltank. The beam 104 also carries a gearchange lever 109 which connectswith the selector cam drum assembly 87 of the transmission system bymeans of a rod 110, which runs in a tube 111 through the fuel tanksection 108 of the beam 104.

A power unit assembly as described above with reference to the drawingswould offer numerous advantages. Whilst many of the features areindividually advantageous, they are especially intended to be mutuallycomplementary and contributory to a design in which engine, auxiliary,transmission, suspension and mounting components are all fullyintegrated into a particularly compact, lightweight assembly, with nosacrifice of optimum transmission or induction system efficiency, havinga low centre of gravity, advantageous mounting characteristics and afavourable gearchange arrangement, and which yet offers benefits interms of manufacturing cost. Such an assembly would facilitate thedesign of cars which are more compact, light and fuel efficient,particularly high performance cars and especially sports cars.

I claim:
 1. In or for a self-powered vehicle, a power unit comprising:acasing structure for said power unit; a reciprocating piston internalcombustion engine comprising a plurality of pistons working in aplurality of cylinders disposed in line, whereby the axes of saidcylinders are parallel and lie in a common first plane, a crankcase, anda crankshaft rotatable within said crankcase about an axis and driven bysaid pistons; a transmission system comprising a plurality ofgearcarrying shafts including an input shaft, and two coaxial outputshafts adapted respectively to drive two wheels located to oppositesides of said power unit, said axes of said output shafts beingsubstantially parallel to said crankshaft axis, and said input shaftbeing in driving communication with said crankshaft; a second planelying at right angles to said common first plane and including saidcrankshaft axis, said transmission system being arranged alongside saidcylinders and so that said input shaft, said output shafts and saidcylinders all lie to the same side of the said second plane; said casingstructure including a casing part within which said cylinders arelocated, in which a first plane joint face is presented by said casingpart and is substantially co-planar with said axis of said outputshafts, and including a cylinder head adapted to engage with said firstplane joint face.
 2. In or for a self-powered vehicle, a power unitaccording to claim 1 in which said casing structure includes a maincasing component, said component including first and second regions, inwhich said cylinders lie within said first region and parts of saidtransmission system lie within said second region.
 3. In or for aself-powered vehicle, a power unit according to claim 1 in which saidcasing structure also includes cover means for said crankcase and for apart of said transmission system adjacent said crankcase, and in whichsaid casing structure presents a second plane joint face against whichsaid cover means engage.
 4. In or for a self-powered vehicle, a powerunit according to claim 3 in which said crankshaft axis is substantiallyco-planar with said second plane joint face.
 5. In or for a self-poweredvehicle, a power unit according to claim 3 in which said first andsecond plane joint faces are parallel.
 6. In or for a self-poweredvehicle, a power unit according to claim 1 including cover means for thepart of said transmission system in which said output shafts arelocated, and in which said cover means engage with said casing structurein the plane of said first plane joint face.
 7. In a self-poweredvehicle, a power unit according to claim 1 in which said vehiclepresents a longitudinal centre line and said pair of driven wheelslocated symmetrically one to each side of said centre line so as to belocated on a common virtual axle, in which said engine is located sothat said plurality of cylinders are disposed to either side of saidcentre line in a substantially symmetrical manner, in which saidtransmission output shaft is substantially coincident with said virtualaxle at the normal ride height of said vehicle, in which means ofconnection of each of said pair of wheels to each of said output shaftsrespectively include universally-jointed drive shafts and in which saidtransmission is located substantially vertically beneath said enginewithin said casing.
 8. In a self-powered vehicle, a power unit accordingto claim 7 in which each said wheel of said pair presents a wheel hubspindle, including a suspension system for said pair of driven wheels,said suspension system comprising for each wheel a supporting linkageincluding lower and upper transverse members and a wheel-carryingmember, in which for each wheel said universally-jointed drive shaftacts as said lower transverse member, bearings in said wheel-carryingmember support said hub spindle, and said upper transverse member isrigid and there are connections between one end of said transversemember and said wheel-carrying member and between the other end of saidrigid member and said casing structure, said connections being in theform of pivots the axes of which lie substantially parallel to thedirection of rolling of said wheel.
 9. In or for a self-powered vehicle,a power unit according to claim 1 in which said transmission system alsoincludes a layshaft arranged parallel to said input and output shafts,and including at least two gear pairs of differing ratio, said gearpairs being alternatively engageable and each gear pair comprising adriving gear coaxial with said input shaft and a driven gear coaxialwith said output shafts, and including also at least one further gearpair engageable to provide drive from said input shaft to said layshaft,a rotary part coaxial with said input shaft, and gearing meansengageable to provide drive back from said layshaft to said rotary part.10. In a self-powered vehicle having front and two rear road wheels anda compartment containing seats, a power unit according to claim 1 inwhich said engine is installed adjacent to said rear wheels and withsaid crankshaft lying transversely relative to said vehicle, in whichone end of a substantial beam is fixed to said casing and extendsforwards, in which a flexible mounting connects the other end of saidbeam with said vehicle at a location transversely central relative tosaid vehicle and longitudinally forward of said seats, and in which twofurther flexible mountings, transversely close to each of said two rearwheels of said vehicle respectively connect said engine to said vehiclestructure at locations longitudinally rearward of said seats.
 11. In orfor a self-powered vehicle having rear and two front road wheels and acompartment containing seats, a power unit according to claim 1 in whichsaid engine is installed adjacent to said front wheels and with saidcrankshaft lying transversely relative to said vehicle, in which one endof a substantial beam is fixed to said casing and extends rearward, inwhich a flexible mounting connects the other end of said beam with saidvehicle at a location transversely central relative to said vehicle andlongitudinally rearward of said seats, and in which two further flexiblemountings, transversely close to each of said two front wheels of saidvehicle respectively, connect said engine to said vehicle structure atlocations which are longitudinally forward of said seats.
 12. In or fora self-powered vehicle, a power unit comprising:a casing structure forsaid power unit; a reciprocating piston internal combustion enginecomprising a plurality of pistons working in a plurality of cylindersdisposed in line, whereby the axes of said cylinders are parallel andlie in common first plane, a crankcase, and a crankshaft rotatablewithin said crankcase about an axis and driven by said pistons; atransmission system comprising a plurality of gearcarrying shaftsincluding an input shaft, and two coaxial output shafts adaptedrespectively to drive two wheels located to opposite sides of said powerunit, said axes of said output shafts being substantially parallel tosaid crankshaft axis, and said input shaft being in drivingcommunication with said crankshaft; a second plane lying at right anglesto said common first plane and including said crankshaft axis, saidtransmission system being arranged alongside said cylinders and so thatsaid input shaft, said output shafts and said cylinders all lie to thesame side of the said second plane; said casing structure including acasing part within which said cylinders are located, in which a firstplane joint face is presented by said casing part and is substantiallyco-planar with said axis of said output shafts, and including a cylinderhead adapted to engage with said first plane joint face; said power unitfurther including a connection between the parts of said casingstructure encasing said engine and said transmission system, whereby, inuse, the said part encasing said transmission system will serve as alubricant sump for said engine, said connection being in the form of apassage formed within said casing structure itself.
 13. In or for aself-powered vehicle, a power unit according to claim 12 in which saidpassage enters said part of said casing unit which encases said engineadjacent said crankshaft, in a direction substantially tangential to therotary motion of said crankshaft.
 14. In or for a self-powered vehicle,a power unit comprising:a casing structure for said power unit; areciprocating piston internal combustion engine comprising a pluralityof pistons working in a plurality of cylinders disposed in line, wherebythe axes of said cylinders are parallel and lie in a common first plane,a crankcase, and a crankshaft rotatable within said crankcase about anaxis and driven by said pistons; a transmission system comprising aplurality of gearcarrying shafts including an input shaft, and twocoaxial output shafts adapted respectively to drive two wheels locatedto opposite sides of said power unit, said axes of said output shaftsbeing substantially parallel to said crankshaft axis, and said inputshaft being in driving communication with said crankshaft; a secondplane lying at right angles to said common first plane and includingsaid crankshaft axis, said transmission system being arranged alongsidesaid cylinders and so that said input shaft, said output shafts and saidcylinders all lie to the same side of the said second plane; said casingstructure including a casing part within which said cylinders arelocated, in which a first plane joint face is presented by said casingpart and is substantially co-planar with said axis of said outputshafts, and including a cylinder head adapted to engage with said firstplane joint face, said vehicle presenting a longitudinal center line anda pair of driven wheels located symmetrically one to each side of saidcenter line so as to be located on a common virtual axle, in which saidengine is located so that said plurality of cylinders are disposed toeither side of said center line in a substantially symmetrical manner,in which said transmission output shaft is substantially coincident withsaid virtual axle at the normal right height of said vehicle, in whichmeans of connection of each said pair of wheels to each of said outputshafts respectively include universally-jointed drive shafts and inwhich said transmission is located substantially vertically beneath saidengine within said casing, said engine having a lower side, said powerunit further including fuel inlet ports to said engine, said fuel inletports being located on the lower side of said engine adjacent to saidtransmission system and an induction tract for said engine beingprovided and which enters said engine at a location on the lower sidethereof which is adjacent to said transmission system, and in which saidinduction tract as it extends away from said engine passes over the partof said casing structure containing said transmission system and thendescends, so that the free end of said induction tract is verticallylower than said location at which said tract enters said engine.